Bimetal thermostat



BIMETAL THERMOSTAT Filed April 23 1950 W// &\

/2 Q 714' +60 [2 all WITNESSES: I INVE-NTOR'V g) Howard 60077? ATTORNEY Patented Mar. 21 1933 UNITED STATES PATENT OFFICE- HOWARD SCOTT, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR T WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, CORPORATION OF PENNSYLVANIA BmETAL .THERMOSTAT Application filed April 23,

My invention relates to thermal devices and particularly to bi-metallic thermostats. 7 An object of my invention is to provide a bi-metallic thermostat that shall have substantially all of the following characteristics; first, that it shall be operable up to a relatively high temperature; second, that it shall have a relatively high sensitivity or deflection over a predetermined and rather large range of temperature; third, that it shall be easily rolled or otherwise fabricated.

In practicing my invention, I provide a bi-metal thermostat including a high-expansion member containing a major portion of iron, appreciable but minor quantities of manganese and nickel, and relatively small quantities of silicon and carbon, while the low expansion member is an alloy containing a major portion of iron, minor quantities of nickel and cobalt and very small quantities of manganese and-carbon.

The single figure. of the drawing is a sectional view of a bi-metal bar embodying my invention.

Since. the operating temperatures to which bi-metallic thermostats are being subjected are increasing, it is necessary .to provide a combination of high-expansion and low-expansion members which shall not lose their strength at relatively high temperatures, and shall have a composition which will ensure that the thermostat will operate in the same manner and to the same extent even after a 15 relatively large number of cyclic operations. I have found that austenitic iron alloys have high expansivity and high strength at the higher temperatures, and an alloy of this kind may be obtained by alloying a major portion of iron with minor portions of mangan'esc and nickel and lesser quantities of silicon and carbon. Carbon can be used inalloys of this kind in relatively small quantities only because, if it is used in larger quantities, it introduces non-reversible expansion 1930. Serial No. 446,776.

take any one of a number of forms.

Herewith is a table of representative combinations of materials used in the high-expansion member and in the low expansion member, respectively, of my new bi-metal combination.

High-ewpansion member No. Pei;4 01am; Perscieut Paroeent Pexiqcient Remainder 51) 12-22. 0.1-0.5 0.1-0.3 1-5 Fe+impur. 2) 13. 5 0. 2 0. 2 5. 9 Fe+lmpu1'. (3) 20.0 0.2 0.2 3. Fe+impur. (4) 17. 0 01 0. 4 5. Fe+impur. 12.0 0.1 0.2 8. Fe-Hmpur. 6) 10.0 0.1 0.2 10.0 Fe-i-impur.

Low-expansion member Percent Pei1 Zent F011; I (gut Perient Remainder V (1) 41.45. 2.0 0. 2-0.9 o-a-s Fe+impu1z 2) 42. 0 2. 0 0.7 0. 1 Fe+impur. 3) 44. 0 2. 0 0. 7 0. 1 Fe+impur. 4) 26. -30. 11.-19. 0. 2-0.9 0 1-0.3 Fe+impur. (5) 27. 3 14. 2 0. 7 0. 1 Fe+im 'ur. (0) 26. 7 17. 3 1 0. 7 0. 1 Fe-Hmpur. g7) 29.4 .120 0.2 0.1 Fe-i-impur. 8) 2s. a 15. 7 0. 2 0. 1 Fe -im ur.

I have found that the addition of nickel to a ferrous alloy containinga minor percentage of manganese has the efi'ect of substantially eliminating the delta -to gamma transformation of the iron within the temperature range of from 0 C. to substantially 500 0., and I have found that combinations of alloys such'as are set forth in the tables here- -inbefore given can be easily fabricated, that is, rolled, fonthe reason that the hardnessof the two elements is substantially the same. The deflection of such bi-metal combinations H i is relatively high, but the major characteris tic which is inherent in these alloys is that of improved Work hardening properties so that it is much easier to manufacture and fabricate bi-metals of this kind than has been possible heretofore.

Various modifications may be made in the device embodying my invention and I desire, therefore, that it shall be limited only by the appended claims.

I claimas my invention:

1. A thermostatic element comprising a pair of cooperating metallic members having different temperature coefficients of expansion, the high-expansion member including approximately sixteen per cent of manganese,

' a major portion of iron, relatively small quantities of silicon and carbon and ap roximately three per cent of nickel to su tantially eliminate the delta to gamma transformation of the iron within the temperature range of from 0 C. to 500 'C., and the low-expansion member being an iron alloy including approximately twenty-eight per .cent nickel, approximately sixteen per cent cobalt and not over one per cent each of manganese and carbon.

2. A thermostatic element including a pair of cooperating metallic members havlng different temperature coefficients of expansion, the high-expansion member having substantially the following composition, a I I Per cent Manganese 10 to22 4o Nickel t0 Silicon .01 to .5 Carbon .1 to .4 Iron remainder and the low-expansion member having sub stantially the following composition Per cent Nickel 26 to 45 Cob l 2 .to 19 Mang n .2 to .9 Carbon .1 to .3 Iron 1. remainder.

In testimony whereof, I have hereunto subscribed my name this 18th day of April 1930. HOWARD SCOTT. 

